Monday, 7 October 2013

Mendel90 Lasercut - Overview

Thanks for all the interest we have been getting for the new Lasercut Mendel90! This post is to give an overview for those new to 3D printers and answer questions about how easy the M90LC is to assemble. It is not designed to replace the detailed assembly instructions and user manual which are now awaiting final feedback from our beta testers before being published.

Printer Overview

The Mendel90 Lasercut is a RepRap printer: there is much more information about RepRaps in general on the wiki but in summary it is a printer which can print the plastic parts that go into its assembly along with many other interesting and useful things. To get an idea of what people are using RepRap-style printers for, a good place to look is Thingiverse. Most CAD and 3D design software can export ".stl" files which the printing software uses to generate print instructions. The printer works by laying down layers of plastic, one on top of the other, to build up an object, in a process called fused filament fabrication.The Mendel90 lasercut has a build area of 200mm x 200mm x 200mm and comes with a single 0.4 mm extruder nozzle which can reliably print layers as thin as 0.1mm. With a smaller extruder nozzle it can reliably print as low as 0.02mm.Looking at the printer from the front, the Mendel90 LC axis are X left and right, Y backwards and forward and Z up and down. The print head is in the 0,0,0 position when it is fully to the left (X=0), the heatbed is fully to the back (Y=0) and it is just touching the surface of the glass on the heatbed (Z=0). The "homed" or parked printhead position is at 200,200,200.

The electronics are mounted at the right buttress along with the power supply unit. They support the addition of other types of electronics in future upgrades.

General points

The printer is made up of sub-assemblies which need to be completed before each major part of the printer is assembled. The sub assemblies can, in general, be worked on in parallel if more than one person is assembling the printer, reducing the build time.

The printer design in regularly updated, so refer to the manual that is distributed with your printer for the most up to date instructions.

The next section will provide an overview of the assembly process

Tools

Spanners/sockets: 5.5mm, 7mm & 13mm.

Allen keys: 1.5mm, 2mm, 2.5mm, 3mm

PZ 1 Pozidriv screw driver and 2mm slotted screwdriver

Digital callipers

Lithium/PTFE grease, glass cleaner (acetone recommended).

Multi-meter (optional)

X axis sub-assemblies

The X Idler and Motor brackets are the interface between the X axis and the Z axis and are the most complex sub-assemblies.

X Idler

X Motor

The X Carriage runs on the X rods between each motor end, and the extruder and fan are attached to it

X Carriage

Extruder Fan

Extruder

Y axis sub-assemblies

In comparison the Y axis and its sub assemblies are simpler.

Y Idler

Y Motor

Y Carriage

Z axis sub-assemblies

Similarly the Z sub-assemblies are quick to put together.

Z Endstop

Z Motor Boxes

Z Top Brackets

Frame Assembly

Once the sub assemblies are done the frame slots together using square captive nuts and M3 fasteners.

First the buttresses, back-top and extruder "sandwich" are assembled:

Then the portal and motor boxes are added:

Finally the base and the aluminium channels are fixed on:

The assembled frame:

Y Axis Assembly

The Y Axis runs along the base and is the first axis to be assembled onto the frame, starting with the bar clamps

Then the motor, rods and the Y axis assembly are added. This assembly sequence allows for the belt to be a pre-set length and for the rods clamps to be tightened with the axis in place to ensure it runs true

A heat shield is added before the bed is fixed above it.

Note how the electrical connections are pre-terminated for quick assembly. Strain relief is built into all the parts where required and ribbon cables are formed into defined and controlled bends between all moving and static cable attachment points.

Z and X Axis Assembly

As noted earlier, the X Axis idler and motor brackets are the interface between the Z and X axis and these axes are assembled together.

First the Z top brackets are fitted, then the smooth rod is fed down through the X axis idler and motor brackets.The X rods are slid through the X idler and the X carriage.

The Z axis screws are then added and the wiring tidied up,

before the extruder is mounted on the X carriage.

Electronics

By this point all the wires from each motor, endstop and the hotend and heatbed are routed through to the back right of the machine ready for the power supply and printer controller board to be fitted.

The Arduino board and the RAMPS are mounted on the hex pillar standoff before the wiring is plugged in.

At this point the printer is assembled and ready for calibration! This post is long enough already so I will do another one to cover calibration.

Update: The source files on github for the Mendel90 Lasercut have now been modified to include changes to the X Idler and X motor brackets that makes them easier to print and more robust. This is one of a number of changes that have been incorporated from Nophead's latest update to the design.

16 comments:

Hi guys,Nice work. One or two small questions...Why did you need to place a tripple layer bracing piece to the top rear between the two buttresses? Is it adding structural rigidity, or does it have some other function? You have me guessing! And why on earth did you call the piece an "extruder sandwich"? :-)

The extruder "sandwich" is designed to take up to 5 RepRapPro style mini bowden extruders - allowing for multi-colour and multi-material printing. Because this would be a pain to add it later it is designed in from the beginning. I went with the triple layer because I wanted more rigidity than a single layer and the triple layer allowed the fastening scheme to be easier. A double layer would have had two slots joined together which had the potential to be aligned poorly.

The new X carriage design is intended to be modular to support addition of heads as required, but I have still got to do quite a bit of work to confirm the wiring scheme (stay with the M90 ribbon cable and D type connector which I like or not, etc?).

There will be a lot more to come in the next few months and the intention is that all the Mendel90 Lasercut kits that are sold now will have a supported upgrade path to multiple extruders.

Hi Tony,Sounds like you have some great plans there, and the M90 platform is certainly an excellent chassis to base it all on. I look forward to seeing how it evolves.Thanks for sharing. Hope I didn't force you to share plans too early! :-)NumberSix

Great to hear from you again, I remember the conversation. If you check out the web shop linked at the top of the blog all our contact details are there. Among other things my ongoing quest for the ultimate hot end design is ongoing, I have recently been playing with a number of different designs so would be very happy to discuss "machinability" with you.

Its made of Melamine faced MDF. This much harder wearing than regular MDF and allows for the fixing method used in this design. Dibond is also a great material and what Nohead uses in his kits but it would not work well using this fixing method.

The full BOM is here: http://www.think3dprint3d.com/3D-Printer-Kits/Mendel90-Lasercut-kit/#tab-product-tab4which shows what everything is in the kit.

Un protected MDF can moisture warp - our original MDF Mendel90s were all varnished for this reason.

The Melamine coating and laser cut edges minimised the problem - I have noticed no warping at all, even on the v0.1 prototype (still going strong after over a year). That said we use them in a relatively dry environment (worst case is an unheated garage) and also they are used frequently! that compired with the enclosure means they keep dry.

If you were going to make one to use in a very damp/humid environment then Dibond would be much better, but there are other issues as weel to consider such as the choice of metal parts to avoid corrosion.

Hi Tonyhave had a slight problem with our 3 d printer and you dad Roland said to send part back,,which we have done but I cant seem to get in contact with him now and were a bit desperate as we have a few things to print.